Light mortar



- Feb. 28, 1939. O. DONNER 2,148,808

LIGHT MORTAR 1 Filed June 2, 1936 2 Sheets-Sheet l Feb. 28, 1939. o.DQNNER 2,148,808

LIGHT MORTAR Filed June 2, 1956 2 Sheets-Sheet 2 zoo foo

Patented Feb. 28, 1939 UNITED STATES PATENT cfs-Fries Application .lime2, 1936,

Serial N0. 83,114E

In Finland March 28, 1935 2 Claims.

My invention relates to ordnance, and particularly' to mortars.y

It has for an object to produce a mortar of light weight, quick andsimple in its operation 5 and having an adequate shooting range.

In the drawings, whichillustrate one embodiment ofthe invention,

Fig. 1'- is a part side elevationv and part vertical longitudinalsection of mortar embodying the invention.

Fig. 2f is an enlarged detail view of a portion oi the structure showninFig-l.

Fig', 3 is a cross section on the Fig. 2.

A Fig. 4- is a diagram illustrating the action that takes place when mymortar operates.

In most armies the needV of a light 40 to 65 millimetre mortar has beenlong felt. To ull the requirements' of practice the operation of a gunor this kind on the battlefield should, however, be extremely simpleandV quick. For this purpose eii'orts have been made, although with poorsuccess, to fire a winged shell by the use of one single propellantcharge placed in the base of the shell. It has, however, been foundextremely difficult to obtain the large variety of shooting rangessimultaneoush7 required and varying between On regulating the shootingrange by changing the angle of elevation it is necessary to direct thegun almost vertically for short shooting ranges. An elevation range of75, corresponding to half of the maximum shooting range, oiersconsiderable practical drawbacks and in such constructions, in

which the shooting range is regulated by changing the elevation angle ofthe tube, one has to fall back upon the use oi four different auX-iliary propellant charges or relays, in which cases the shooting rangesare 800, 650, 350, 200 and 100 metres respectively. Various efforts havebeen made to simplify the operation of the gun by using a constantelevation angle. A deviation oi 10 or less of the angle of elevationfrom the 43 which correspond to the maximum shooting 45 range is not ofmaterial consequence because of the very small change in the shootingrange caused by this deviation. In this case it is suicient to directthe gun in the direction oi the target and as, on this shooting range,the trans- 50 versal inclination of the pointing device has aconsiderably smaller influence than for large elevation angles, theoperation oi the gun is thus considerably simplified while its accuracyin practice is greatly improved.

55 Leaving, therefore, the regulation of the shootline 3-3 of ing rangeby changing the angle of elevation and by usingl a variable propellantcharge out of consideration as being impracticable, there is stillYavailable regulation byl the aidof the gas leakage opening and the gaschamber behind the shell. tion by the leakage of the gas was in use,among others, in the British and Polish armies, but after ashort periodthev use of this construction was abandoned; The cause for this was that10.. so far it has notY been possible to construct the rathercomplicated mechanism required for thev closing and opening of theopenings fixed points along the tube so that the same would operateaccurately in practice, even with 15;: frequent cleaning. Regulation bythe use of a variabievolume ofthe gas chamber behind the projectile hasllikewise been' employed in a construction, in which the starting pointoi the projectile was-pushed slightly forward to obtaina 2Q larger gaschamber.

As a slightly enlarged gas chamber reduces considerably the gaspressure, this systeml has certain advantages, among others, by reducingthe dispersion in firing at medium shooting 2,5 ranges. Although aVslight displacement of the l" starting point ofthe projectile has, atthe beginning, a relatively great influence on the shooting range, thecontinued displacement of the same is of less importance. tain accuracy,a certain expansion allowance will further be required and as theplacing of the starting point of the projectile too near to the mouth oithe tube oiers other considerable drawbacks, the regulation according tothis method 35 has been used only in connection with a variablepropellant charge The present invention relates to a construction bywhich the poss'bilities of regulation by the aid of the gases forlargely diierent shoot- 40 ing ranges are combined with the advantagesof a variable volume of the gas chamber, of a low pressure and of theaccuracy obtainable on medium shooting ranges without requiring anymechanism for the opening and closing of the gas openings and thedrawbacks adhering therein. In principle the invention is based upon thefact that the starting point of the projectile in the tube may bechanged, for instance, by the aid of an adjustable percussion pin.During the iirst stage of this movement the shooting range is regulatedchiefly by enlarging the gas chamber, When the projectile is furtherdisplaced, the girdle of the same will close one or more of the gasopenings which are, generally, con- 5| As, to obtain a cer- 30 I stantlyopen. If the starting point is near to the rear end of the tube, thespeed of the projectile on passing theopenings will be great and theperiod of time during which the gases may leak through the openings willbe relatively short; further, the gases are to some extent cooled by thework effected by them. The influence of the openings is, in this case,relatively small.

On the other hand, when the starting point of the projectile is near tothe rst opening, the speed of the projectile is smaller and theinfluence of the openings many times greater. When, nally, the startingpoint of the projectile is still more advanced, the girdle of theprojectile will, from the start of the movement, bare theopening oropenings so that the projectile as a Whole will operate in the samemanner as a plunger vane in a gas regulating device and thus enable theattaining of the shorter shooting ranges.

In the drawings T designates the tube of the mortar which is providedwith the various leakage openings, O1, O2, O3, etc. The percussion pinis indicated by S, While V is a crank to turn the bevel gear a andthereby turn the bushing b through meshing gear g. P1 the variousstarting points of the tube. The pin S has a sleeve c which is caused torotate by means of a stud and slot connection h between the sleeve c andthe bushing b.

direction or the other.

In Fig. 2 the curves K illustrate the eiect vof the change of thestarting point of the pro--V between and 700 metres.

I claim: 1. In a light mortar of the character described, closing thelower end of the will act to close selected leakage openings, said meanscomprising a rotatable bushing, a crank operated device for rotatingsaid bushing, means to connect said bushing and said sleeve together invirtue of which the sleeve may be turned about 2. In a light mortar inerally effected with one simple principal powder said means including aloncated normally in advance of the shell to be red., and means sleeveto position yet be free to move longitudinally, and a xed screw spindlein threaded engagement With said sleeve, 1n virtue

